Arc plates having resilient flanges



United States Patent ARC PLATES HAVING RESILIENT FLANGES Allen E. Stringfellow, Haddonfield, N.J., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Mar. 15, 1957, Ser. No. 646,259

3 Claims. (Cl. 200-144) This invention relates to are plates used in the arc chutes of power circuit interrupters and more particularly to ceramic arc plates having resilient flanges.

One prior art method of spacing are plates consists of nesting the plates within slots cut in the opposed inner side surface of the arc chute shell. A second method of spacing consists of molding arc plates having integrally formed ribs on each of the long sides of the plate. While a third means of spacing consists of running asbestos rope along both long edges between the plates and then compressing the stack along the edges thereof until the proper spacing has been achieved.

In each of the aforesaid methods the long edges of the arc plates are rigidly fixed in position and because of this the thin unsupported body portion of the arc plate would often be fractured by the mechanical forces accompanying the circuit interrupter. In the case of the asbestos rope as a spacing means, if the rope is not fully compressed in spacing the arc plates it will be further compressed by the arc forces. However, since the asbestos rope is not resilient it will not return the plates to their designed spacing so that the arc chute will not be as effective in extinguishing subsequent arcs. Furthermore, the rigid spacing means results in a high reject rate of the arc plates because of warpage and camber.

My invention comprises a resilient means to space the ceramic plates of an arc chute. In one embodiment the resilient means is preformed into an elongated member having a U-shaped cross-section. The resilient elongated member is then pressed over one or both of the long edges of the ceramic arc plate to form flanges which extend beyond the front and back surfaces of the plate. In a second embodiment a resilient flange is formed along one or both long edges of the arc plate to extend above either or both the front and back surfaces and is then cemented to the plate.

The ceramic plates with the resilient flange spacers are then stacked. Pressure is applied to the stack until the flanges are compressed to approximately of their original size. The compressed stack is then placed in an arc chute shell where the plates are held firmly but gently by the partially compressed resilient spacing means.

The resilient spacers act as springs which absorb the shock forces accompanying arc formation and serve to prevent the relatively brittle ceramic are plates from breaking and cracking. Since the spacers are resilient they will compensate for plate variations without overstressing any particular point in the plate thereby permitting a greater warpage tolerance in the plate manufacture. Furthermore, the resilient spacers form a good seal between plate thus preventing ionized gases from flowing along the sides of the shell and short circuiting the arc chute.

The resilient material preferably comprises a MgO-SiO ceramic fiber which is sold under the trade name Fiberfrax, while the cement which secures the resilient material to the ceramic arc plate is comprised of sodium silicate or any fine grained refractory cement. This material, in addition to being resilient, is inorganic and noncarbonizing, possesses a high dielectric, and is capable of withstanding high temperatures.

Accordingly, a primary object of my invention is to provide resilient means for spacing the arc plates of an arc chute with the spacers also acting to absorb the impact of the forces accompanying arc formation.

Another object is to provide ceramic arc plates having one or more resilient flanges cemented thereto.

Still another object is to provide ceramic arc plates having resilient members of U-shaped cross-section overlying one or both of the long edges of the plates.

These and other objects of my invention will become apparent after reading the following description and considering the accompanying drawings in which:

Figure l is" a plan view of a ceramic arc plate having U-shaped resilient members overlying the edges thereof.

Figure 2 is an end view of Figure 1 looking in the direction of arrows 22.

Figure 3 is a cross-section of a U-shaped resilient member.

Figure 4 is an end view of another embodiment of my invention wherein the resilient member is formed over the edge of the arc plate and then cemented in place.

Figure 5 is an end view of another embodiment of my invention wherein the resilient material is cemented to one side of the ceramic arc plate.

Referring to Figures 1-3, are plate assembly 10 comprises a thin flat arc plate 11 of ceramic or other insulating material and resilient flange members 16 overlying each of the long edges 17 of the arc plate 11. Are plate 11 includes an arcing slot 12 having a first wide width section 13, a second intermediate width section 14, and a third narrow width section 15 wherein the arc is forced to be squeezed and lengthened to be rapidly extinguished as fully explained in copending application 322,027, filed November 22, 1952, and assigned to the assignee of the instant invention, now issued as Patent Number 2,759,073.

Resilient flange members 16 are strip like members out to the length of the arc plate 11 and having a preformed substantially U-shaped cross section so that they may readily be installed on and secured to are plate 11. Before being installed on the arc plate 11, the arms 28 and 29 of each flange member 16 converge slightly so that they are more closely spaced at the mouth 30 of depression 32 than they are at the bottom 31 of depression 30. The arms 28 and 29 must be spread slightly to install resilient flange members 16 on the arc plate 11 which puts a slight loading on the resilient material of the flange members 16 so that they will grip the arc plate 11 and provide suflicient friction so that the resilient flange members 16 are secured to the arc plate 11 with sufficient tenacity. Flange members 16, being resilient, will readily compensate for manufacturing defects such as warp-age, camber, and surface irregularities in arc plates 11. A suitable material for the fabrication of flange members 16 is known as Fiberfrax which is a ceramic fiber product of the Carborundum Company.

When a plurality of arc plate assemblies 10 are stacked, the arc plates 11 will be separated by the double thickness of arms '28 or 29. The stacked arc plate assemblies are then compressed to about of their thickness and the stack is inserted into the shell of an arc chute (not shown). When are forces hit the chute the arms 28 and 29, being further compressible, will absorb most of the shock thus preventing the arc plates from cracking and breaking.

Resilient flange member 16 being of U-shaped crosssection provides two flanges 28 and 29 for each long edge 17 of arc plate 11. It can readily 'be seen that are plate assembly including flat arc plate 11 having a resilient flange member 16 overlying but one long edge 17 would be suitable for a stack of parallel arc plates spaced by a single thickness of arms 28 or 29.

-A second embodiment of my invention is illustrated in Figure 4. Are plate assembly 40 comprises arc plate 11 having resilient flange members 18 overlying each long edge 17. Flange member 18 differs from flange member 16 in that the former is not preformed but instead is made from a flat strip folded over the long edges 17 to assume a U-shape. The ends of the U-arms are cemented at 19 to the arc plate 11 to form are plate assembly 40. A plurality of arc plate assemblies 40 are assembled and placed in a shell to form an arc chute in the same way as were are plate assemblies 10 with their reactions to the forces accompanying arcing being the same.

A third embodiment of my invention illustrated in Figure comprises arc plate assembly 50 which includes arc plate 11 having two resilient flange members 20 cemented thereto at points 21 on the bottom surface 49 and running for the entire length of arc plate 11. Another two resilient flange members 20 may be cemented to the top surface 48 in line with flange members 20 on the bottom surface to thereby convert arc plate assembly to the equivalent of arc plate assemblies and 40.

Are plate 11 with two resilient flange members 2%) cemented thereto along any combination of top surface 48, bottom surface 49, and the long edges 17 is the equivalent of arc plate 11 having but one resilient flange member 16 or 18 secured thereto. That is, each arc plate now includes two resilient flanges so that when stacked the arc plates will be resiliently supported along both long sides in spaced parallel.

Thus I have provided an arc plate assembly including resilient flanges for spacing and supporting which are readily assembled from easily manufactured components.

In the foregoing, I have described my invention only in connection with preferred embodiments thereof. Many variations and modifications of the principles of my invention within the scope of the description herein are obvious. Accordingly, I prefer to be bound not by the specific disclosure herein but only by the appending claims.

I claim:

1. An arc plate assembly comprising a first and second flat elongated arc plate having a pair of substantially parallel long edges; each of said first and second flat arc plates having a resilient flange secured thereto; each of said resilient flanges being positioned adjacent at least one of said long edges of their respective flat arc plate; said flanges resiliently spacing said first and second arc plate with respect to one another; said resilient flanges being removable with respect to said first and second flat arc plates; said resilient flanges comprising a striplike member having a substantially U-shaped cross-section; said resilient flanges overlying said one of said long edges of said respective flat arc plates.

2. An arc plate assembly comprising a first and second flat elongated arc plate having a pair of substantially parallel long edges; each of said first and second flat arc plates having a resilient flange secured thereto; each of said resilient flanges being positioned adjacent at least one of said long edges of their respective flat arc plate; said flanges resiliently'spacing said first and second arc plate with respect to one another; said resilient flanges being removable with respect to said first and second flat arc plates; said resilient flanges comprising a strip-like member having a substantially U-shaped cross-section; said resilient flanges overlying said one of said long edges of said respective flat arc plates; the arms of said U- shaped cross-section converging when said resilient flanges are detached from said are plate.

3. An arc plate assembly comprising a firstand second fiat elongated arc plate having a pair of substantially parallel long edges; each of said first and second flat arc plates having 'a resilient flange secured thereto; said resilient flanges being positioned adjacent at least one of said long edges of their respective flat arc plate; said flanges resiliently spacing said first and second arc plate with respect to one another; said resilient flanges being removable with respect to said first and second flat arc plates; said resilient flanges comprising a strip-like member having a substantially 'U-shaped cross-section; said resilientflanges overlying said one of said long edges of said respective flat arc plates; the arms of said U-shaped cross-section converging when said resilient flanges are detached from said are plate; said resilient flanges being comprised of a ceramic fibre material.

References 'Cited in the file of this patent UNITED STATES PATENTS 417,647 Kling Dec. 17, 1889 2,442,199 Dickinson et al. May 25, 1948 2,692,319 Dickinson et al. Oct. 19, 1954 2,708,698 Ainsworth May 17, 1955 2,759,073 Wood Aug. 14, 1956 2,864,919 String'fellow Dec. 16, 1958 FOREIGN PATENTS 1,128,986 France Sept. 3, 1956 

